Apparatus and method for cancelling inter-cell interference in communication system

ABSTRACT

The present disclosure relates to an apparatus and method for canceling and/or suppressing inter-cell interference in a wireless communication. The method includes: establishing a Radio Resource Control (RRC) connection with a base station through a first serving cell; receiving, at a User Equipment (UE), an RRC message through the first serving cell, the RRC message comprising cell-specific reference signal (CRS) information of a neighbor cell and Physical Downlink Shared Channel (PDSCH) information of the neighbor cell, and the PDSCH information of the neighbor cell comprising a parameter relating to a power ratio of a CRS of the neighbor cell and a PDSCH of the neighbor cell; receiving the PDSCH through the first serving cell; performing a channel estimation for retrieving data from a PDSCH of the first serving cell; and retrieving the data from the PDSCH of the first serving cell based on the second channel estimation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of a U.S. patent application Ser. No.14/530,501, filed on Oct. 31, 2014, which claims priority from and thebenefit of Korean Patent Application No. 10-2013-0132109, filed on Nov.1, 2013, each of which is hereby incorporated by reference in itsentirety.

BACKGROUND

1. Field

The present disclosure relates to a wireless communication, moreparticularly, to an apparatus and method for canceling or reducinginter-cell interference in a wireless communication system.

2. Discussion of the Background

In general, in a multi-cellular communication system, each cell does notconsider other cells and when a base station and a user equipmentcommunicate with each other while maintaining frequency reuse as ‘1’ atthe same time and in the same frequency band, a UE that is positioned tobe closer to a cell boundary is significantly degraded due to distortionof a signal caused by power reduction of a received signal andinterferences from other cells

Various techniques have been researched up to now in order to overcome aperformance degradation phenomenon by the power reduction and theinterferences and as one technique thereof, a coordinated multiple point(CoMP) scheme in which multiple cells or multiple transmission terminalsare coordinated with each other has been discussed. The coordinatedmultiple point scheme (CoMP) may also be called a cooperativetransmission and reception scheme. The CoMP generally designates amethod in which different base stations or multiple transmissionterminals are coordinated with each other to perform communication withthe same UE. That is, in the above scheme, a plurality of base stationsshare information on a cell and performs downlink transmission or uplinkreception. The CoMP includes the case in which the plurality of basestations are coordinated with each other to perform downlink or downlinkscheduling in order to efficiently distribute radio resources.

This scheme can improve a transmission power gain and signal and signalsensitivity of UEs having the lower strength of the signal than a UEthat is positioned in a central region of the cell in a region wheresignal receiving sensitivity is high because the UEs are positioned in acell-edge region or a region where the signal receiving sensitivity islow and improve transmission rate of an entire system by effectivelyremoving an influence by interference.

However, according to this scheme, since reference signals (hereinafter,referred to as RSs) cannot be blanked, there is a problem thatinterferences a cell-specific RS (CRS) and a CSI-RS transmitted from theCoMPs are not removed.

SUMMARY

Exemplary embodiments of the present invention relates to an apparatusand method for canceling or reducing inter-cell interference in awireless communication system.

An exemplary embodiment of the present invention provides a method ofperforming a wireless communication in an inter-cell interferenceenvironment, the method including: establishing a Radio Resource Control(RRC) connection with a base station through a first serving cell;receiving, at a User Equipment (UE), an RRC message through the firstserving cell, the RRC message including cell-specific reference signal(CRS) information of a neighbor cell and Physical Downlink SharedChannel (PDSCH) information of the neighbor cell, and the PDSCHinformation of the neighbor cell including a parameter relating to apower ratio of a CRS of the neighbor cell and a PDSCH of the neighborcell; receiving the PDSCH through the first serving cell; performing achannel estimation for retrieving data from a PDSCH of the first servingcell.

The channel estimation includes: performing a first channel estimationfor the PDSCH of the first serving cell based on a CRS of the firstserving cell; based on interference information of the CRS of theneighbor cell, canceling an interference of the CRS of the neighbor cellfrom the first channel estimation; and based on the parameter relatingto the power ratio of the CRS of the neighbor cell and the PDSCH of theneighbor cell, performing a second channel estimation for the PDSCH ofthe first serving cell by canceling an interference of the PDSCH of theneighbor cell. The method retrieves the data from the PDSCH of the firstserving cell based on the second channel estimation.

An exemplary embodiment of the present invention provides a method ofperforming a wireless communication in an inter-cell interferenceenvironment, the method including: establishing a Radio Resource Control(RRC) connection with a User Equipment (UE) through a first servingcell; transmitting, to the UE, an RRC message through the first servingcell, the RRC message including cell-specific reference signal (CRS)information of a neighbor cell and Physical Downlink Shared Channel(PDSCH) information of the neighbor cell, and the PDSCH information ofthe neighbor cell including a parameter relating to a power ratio of aCRS of the neighbor cell and a PDSCH of the neighbor cell; andtransmitting the PDSCH through the first serving cell.

The parameter relating to the power ratio of the CRS of the neighborcell and the PDSCH of the neighbor cell is configured for the UE tocancel an interference of the PDSCH of the neighbor cell in retrievingdata from the PDSCH of the first serving cell.

As inter-cell interferences of a wireless communication system areremoved or suppressed, transmission performance of a PDSCH is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system according to anembodiment of the present invention;

FIG. 2 is a diagram illustrating a communication system that supports acoordinated multiple point scheme;

FIG. 3 is a diagram for describing one example of a system operatingscenario according to the coordinated multiple point scheme;

FIG. 4 is a diagram illustrating an interference situation under anenvironment to which the coordinated multiple point scheme is notapplied;

FIG. 5 is a diagram illustrating an interference situation under anenvironment to which the coordinated multiple point scheme is applied;

FIG. 6 is a diagram illustrating one example of a situation in which aninterference occurs by a CSI-RS under a CoMP environment;

FIG. 7 is a flowchart illustrating an operating sequence of a UE forremoving inter-cell interferences according to the present invention;

FIG. 8 is a flowchart of data for removing the inter-cell interferencesaccording to the present invention; and

FIG. 9 is a block diagram illustrating a UE and an eNB according to oneexample of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Herein, some embodiments will be described in detail with reference tothe accompanying drawings in the present invention. When referencenumerals refer to components of each drawing, it is to be noted thatalthough the same components are illustrated in different drawings, thesame components are referred to by the same reference numerals aspossible. In describing the embodiments of the present invention, whenit is determined that the detailed description of the known art relatedto the present invention may obscure the gist of the present invention,the detailed description thereof will be omitted.

Further, the specification primary describes a communication network,and a task performed in the communication network may be achieved duringa process controlling the network and transmitting data in a system (forexample, a base station) that controls the corresponding communicationnetwork or the task may be achieved in a user equipment linked to thecorresponding network.

Technology described below may be used in various wireless communicationsystems including code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),orthogonal frequency division multiple access (OFDMA), singlecarrier-FDMA (SC-FDMA), and the like. The CDMA may be implemented byradio technology universal terrestrial radio access (UTRA) or CDMA2000.The TDMA may be implemented by radio technology such as Global Systemfor Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). The OFDMA may beimplemented as radio technology such as Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20, E-UTRA (Evolved UTRA), and the like. IEEE 802.16m as theevolution of IEEE 802.16e provides backward compatibility with a systembased on the IEEE 802.16e. The UTRA is a part of a universal mobiletelecommunication system (UMTS). 3^(rd) generation partnership project(3GPP) long term evolution (LTE) as a part of an evolved UMTS (E-UMTS)using evolved-UMTS terrestrial radio access (E-UTRA) adopts the OFDMA ina downlink and the SC-FDMA in an uplink. LTE-advanced (A) is anevolution of the 3GPP LTE.

The LTE-A is primarily described for clear description, but the spiritof the present invention is not limited thereto.

FIG. 1 illustrates a wireless communication system according to anembodiment of the present invention.

Referring to FIG. 1, the wireless communication system 10 is widelyplaced to provide various communication services such as voice, packetdata, and the like. The wireless communication system 10 includes atleast one base station (BS) 11. Each base station 11 provides acommunication service to a specific geographical region or a frequencyregion and may be called a site. The site may be divided into aplurality of regions 15 a, 15 b, and 15 c which may be called a sectorand the sector may have different cell IDs.

A user equipment (UE) 12 may be fixed or movable and may be called otherterms such as a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, and thelike. The base station 11 generally indicates a station that maycommunicate with the UE 12 and may be called other terms such as anevolved-NodeB (eNodeB), a base transceiver system (BTS), an accesspoint, a femto base station (eNB), a home eNodeB (HeNB), a relay, aremote radio head (RRH), and the like. The cells 15 a, 15 b, and 15 cshould be analyzed as a comprehensive meaning representing a partialregion covered by the base station 11 and represents a meaning includingall of various coverage regions including a mega cell, a macro cell, amicro cell, a pico cell, a femto cell, and the like.

The user equipment generally belongs to one cell (that is, acommunication link is configured) and the cell to which the userequipment belongs is referred to as a serving cell. A base station thatprovides the communication service to the serving cell is referred to asa serving base station (BS). Since the wireless communication system isa cellular system, another cell which is adjacent to the serving cell ispresent. Another cell which is adjacent to the serving cell is referredto as a neighbor cell. A base station that provides the neighbor cell isreferred to as a neighbor BS. The serving cell and the neighbor cell arerelatively determined based on the UE.

The embodiment of the present invention may be used in a downlink or anuplink. In general, the downlink means communication from the basestation 11 to the UE 12 and the uplink means communication from the UE12 to the base station 11. In the downlink, a transmitter may be a partof the base station 11 and a receiver may be a part of the userequipment 12. In the uplink, the transmitter may be a part of the UE 12and the receiver may be a part of the base station 11.

The wireless communication system may be any one of a multiple-inputmultiple-output (MIMO) system, a multiple-input single-output (MISO)system, a single-input single-output (SISO) system, and a single-inputmultiple-output (SIMO) system. The MIMO system uses a plurality oftransmit antennas and a plurality of receive antennas. The MISO systemuses a plurality of transmit antennas and one receive antenna. The SISOsystem uses one transmit antenna and one receive antenna. The SIMOsystem uses one transmit antenna and one receive antenna. Hereinafter,the transmit antenna means a physical or logical antenna used totransmit one signal or stream, and the receive antenna means a physicalor logical antenna used to receive one signal or stream.

The wireless communication system may be generally divided into afrequency division duplex (FDD) scheme and a time division duplex (TDD)scheme. According to the FDD scheme, uplink transmission and downlinktransmission are performed while occupying different frequency bands.According to the TDD scheme, the uplink transmission and the downlinktransmission are performed at different timings while occupying the samefrequency band. A channel response of the TDD scheme is substantiallyreciprocal. This means that a downlink channel response and an uplinkchannel response are almost the same as each other in a given frequencydomain. Accordingly, in the wireless communication system based on theTDD, the downlink channel response may be advantageously acquired fromthe uplink channel response. In the TDD scheme, since an entirefrequency bands are time-divided into the uplink transmission and thedownlink transmission, the downlink transmission by the base station andthe uplink transmission by the user equipment may not simultaneously beperformed. In the TDD system in which the uplink transmission and thedownlink transmission are divided by the unit of the subframe, theuplink transmission and the downlink transmission are performed indifferent subframes.

FIG. 2 is a diagram illustrating a communication system that supports anapplicable coordinated multiple point scheme of the present invention.

Referring to FIG. 2, the communication system includes a plurality ofeNB1 200-1, eNB2 200-2 . . . and UE1 210-1, UE2 210-2, and UE3 210-3.

Each eNB provides one cell. The UE 210-1 is positioned at edges of afirst cell Cell1, a second cell Cell2, and a third cell Cell3. The eNB1200-1, the eNB2 200-2, and the Enb3 200-3 as coordinated eNBs transmitsignals to the UE1 210-1 based on the coordinated multiple point scheme.

Each of the coordinated eNBs include a primary eNB (hereinafter,referred to as PeNB) and a secondary eNB (hereinafter, referred to asSeNB). The PeNB has a priority in scheduling among coordinated cells.That is, the PeNB takes the lead in the scheduling in the coordinatedmultiple point scheme and the SeNB performs the scheduling so as toprevent a collision from being occurred in a scheduling resultdetermined by the PeNB. A cell provided by the PeNB is referred to as aprimary cell and a radio link formed by the primary cell and the UE isreferred to as a primary cell link. In addition, a cell provided by theSeNB is referred to as a secondary cell and a radio link formed by asecondary cell and the UE is referred to as a secondary cell link. TheSeNB may be called a neighboring eNB (neighboring BS) or other eNB(other BS). The PeNB may transmit not only downlink schedulinginformation thereof but also downlink scheduling information of theSeNB.

In FIG. 2, the first cell Cell1 is the primary cell in respect to theUE1 210-1 and the eNB1 200-1 is the PeNB. Meanwhile the second cellCell2 and the third cell Cell3 are the secondary cells, and the eNB2200-1 and the eNB3 200-3 are the SeNBs.

FIG. 2 illustrates only one example of performing the coordinatedmultiple point scheme in which the PeNB and the SeNB are coordinated tothe UE positioned at the cell edge and the positions, the number, andthe like of eNBs and cells that perform the coordinated multiple pointscheme. The coordinated eNB may be appropriately determined byconsidering a distance between the UE and the neighboring eNB, an SINR,spectral efficiency, and the like.

FIG. 3 is a diagram for describing one example of a system operatingscenario according to the coordinated multiple point scheme. Thisindicates the case in which the PeNB and the SeNB are dynamicallyconfigured depending on the UE.

Referring to FIG. 3, an eNB1 310, an eNB2 320, and an eNB3 330 aredetermined as the coordinated eNBs. A UE1 341, a UE2 342, and a UE3 343are connected to a cell provided by the eNB1 310 through the primarycell link. A UE4 344, a UE5 345, a UE6 346, and a UE7 347 are connectedto a cell provided by the eNB2 320 through the primary cell link. A UE8348, a UE9 349, a UE10 350, and a UE11 351 are connected to a cellprovided by the eNB3 330 through the primary cell link.

The UE0 340, the UE1 341, and the UE7 347 thereamong are UEs that mayreceive signals from two or more base stations operate in thecoordinated multiple point scheme in order to increase a communicationcapacity. The residual UEs operate not the coordinated multiple pointscheme but a general communication scheme.

The UEs that operate according to the general communication scheme haveonly one primary cell link. For example, the UE2 342 and the UE3 343 areconnected with the eNB1 310 through primary cell links P₂ and P₃,respectively. The UE4 344, the UE5 345, and the UE6 346 are connectedwith the eNB2 320 through primary cell links P₄, P₅, and P₆,respectively. In addition, the UE8 348, the UE9 349, the UE10 350, andthe UE11 351 are connected with the Enb3 330 through primary cell linksP₈, P₉, P₁₀, and P₁₁, respectively.

Since two or more eNBs are coordinated to one UE to performcommunication according to the coordinated multiple point scheme, two ormore cell links are formed. For example, the UE0 340 is connected withthe eNB1 310 through a secondary cell link S₀ and connected with theeNB3 330 through a primary cell link P₀. The UE 341 is connected withthe eNB1 310 through a primary cell link P₁ and connected with the eNB2320 through a secondary cell link S₁. In addition, the UE7 347 isconnected with the eNB1 310 through a secondary cell link S₇ andconnected with the eNB3 330 through a primary cell link P₇.

Although the UE0 340, the UE1 341, and the UE7 347 operate according tothe coordinated multiple point scheme, the PeNB and the SeNB arerelatively determined for each UE. In FIG. 3, the PeNB for the UE0 340is the eNB3 330, the PeNB for the UE1 341 is the eNB1 310, and the PeNBfor the UE7 347 is the eNB2 320.

In the wireless communication system, an uplink channel and a downlinkchannel needs to be estimated for transmission/reception of data,acquisition of system synchronization, feed-back of channel information,and the like. In the wireless communication system, fading occurs due toa multiple-path time delay. A process of restoring a transmission signalby correcting distortion of a signal which occurs by a rapidenvironmental change due to the fading is referred to as channelestimation. Further, a channel state for a cell to which the UE belongsor other cell needs to be measured. The channel estimation is generallyperformed by using a reference signal which a transmitter and a receivermutually know for the channel estimation or the measurement of thechannel state.

Downlink reference signals include a cell-specific RS (CRS), amultimedia broadcast and multicast single frequency network (MBSFN)reference signal, a UE-specific RS, a positioning RS (PRS), and channelstate information (CSI) reference signal (CSI-RS). The CRS as areference single transmitted to all UEs in the cell may be used inchannel estimation for feed-back of a channel quality indicator (CQI)and channel estimation for a PDSCH. The MBSFN reference signal may betransmitted in a subframe allocated to MBSFN transmission. TheUE-specific reference signal as a reference signal received by acell-specific or a specific UE group may be called a demodulation RS(DMRS). The DMRS is primarily used for the specific UE or the specificUE group to demodulate data. The PRS may be used to estimate theposition of the UE. The CRI-RS is used for channel estimation of a PDSCHof a LTE-A UE.

The CSI-RS configuration may be divided into a non-zero transmissionpower CSI-RS configuration indicating a pattern where the CSI-RS istransmitted to the UE of each cell (alternatively, a transmission point(TP)) and a zero transmission power CSI-RS configuration for muting thePDSCH region corresponding to the CSI-RS transmission of a neighbor cell(alternatively, the TP). 0 or 1 CSI-RS configuration is used for the UEassuming the non-zero transmission power CSI-RS, and 0 or several CSI-RSconfigurations may be used for the UE assuming the zero transmissionpower CSI-RS.

Information on one or more non-zero transmission power CSI-RSconfigurations (hereinafter, referred to as the CSI-RS configuration)may be transmitted to each UE of the corresponding cell. Information onthe CSI-RS configuration may include information of 2 bits indicatingwhether the number of antenna ports (hereinafter, referred to as CSI-RSantenna ports) transmitting the non-zero transmission power CSI-RS isone of 1, 2, 4, and 8, and information of 5 bits indicating the CSI-RSpattern which may be configured for each number of CSI-RS antenna ports.

In the embodiment, network assisted interference cancellation andsuppression (hereinafter, referred to as NAICS) assisted by the networkis used. In the NAICS, in order to suppress intra-cell and inter-cellinterference in the receiver side, the network transmits additionalinformation on the interference to the receiver. As compared with atechnique in the transmitter side such as the CoMP which causesdeterioration of performance due to the lack of the channel informationin the transmitter side depending on the limited feedback, the NAICSreceiver has no load on the CSI feedback.

In the NAICS, suppressing the interference due to the PDSCH of theneighbor cell has a high priority. According to the embodiment of thepresent invention, the interference due to the PDSCH may be suppressedby using optimized necessary network information. Further, serious CRSinterference may occur in a new carrier type (NCT) and a small cell.According to the embodiment of the present invention, the CRSinterference may be also efficiently removed.

In this specification, a method for minimizing the interference of thePDSCH, the CRS and the CSI-RS at the UE side based on the NAICS schemeis disclosed. According to the method, the eNB transmits related RSinformation and data symbol power information in order to suppress theinterference of the PDSCH. The method may premise the interference ofthe CRS and the CSI-RS of the neighbor eNB generated in the CoMP scheme.In this case, the eNB may transmit, to the UE, PDSCH rate matching, aquasi co-located (QCL) field, and interference information of the CRSand the CSI-RS of the neighbor eNB to be removed and cancelated.

In order to transmit PDSCH RE mapping and QCL information to the UE, theeNB may configure several PDSCH rate matching and sets of the QCL by aradio resource control (RRC). Different sets indicate different PDSCHstaring points, CRS patterns, and QCL of ZP-CSI-RS and DMRS. The setswhich may be used in the subframe according to the embodiment of thepresent invention may be indicated by a DCI format 2D. Fields to betransmitted to the UE which may be used in the embodiment of the presentinvention is as the following Table 1.

TABLE 1 Field Content n_(CRS) The number of CRS ports 1, 2, 4, andinteger values including preliminary values which are not attached toRel-11 UE form v_(shift) Position on frequency domain of CRS Integer inrange of [0, 5] MBSFN MBSFN subframe configuration subframeconfiguration PDSCH- PDSCH-Start Symbol Start- {0 or preliminary value(FFS), 1, 2, 3, and 4 (4 may be Sym applied only when system BW <=10PRB)as value indicated by PCFICH of serving cell in the case of non-cross-carrier-scheduling or values set in upper layer in the case ofcross-carrier-scheduling zeroTxPower zeroTxPowerResourceConfigList, andZP CSI-RS set value CSI-RS determined by zeroTxPowerSubframeConfig andassumed by PDSCH rate matching and RE mapping of UE QuasiCo Non-zeropower CSI-RS resource index indicated by quasi- Location- colocatgionassumption on DMRS Index

A scenario of the NAICS basically relates to non-ideal backhaul.Accordingly, basically, the CoMP is not, and selectively, the CoMPscheme such as coordinated beamfoaming (CBF) and dynamic point selection(DPS)/DPB may be considered.

Hereinafter, a method for removing or suppressing the interference ofthe PDSCH, the CRS, and the CSI-RS due to the NAICS according to theembodiments of the present invention will be described.

1. Removing Interference in Environment where CoMP is not Applied

FIG. 4 illustrates an example of a situation where interference occursin an environment where the CoMP is not applied. Referring to FIG. 4,cases where the PDSCH is interfered largely include two types. One typeis interference due to the neighbor cell, and the other type isinterference the PDSCH of the neighbor cell. The interference may beremoved or minimized by using optimized information supported by thenetwork. Hereinafter, a method of removing or minimizing the two typesof interference will be described together.

As a semi-static method, the eNB configures one parameter set in orderto indicate the interference due to the CRS and the PDSCH of theneighbor cell to the UE. Herein, the UE may be UE in which the NAICS ispossible. An example of the parameter set is as the following Table 2.

TABLE 2 Parameter set Content CRS interference Scrambling code IDinformation Integer value in range of [0.503] Number of CRS portsInteger value of 1, 2, or 4 MBSFN subframe configuration PDSCH Powerratio of CRS to PDSCH interference PB and PA information Probability(possibility) of modulation scheme

Referring to Table 2, one parameter set includes information of variouscategories. For example, as illustrated in Table 2, the parameter setincludes CRS interference information and PDSCH interferenceinformation.

First, the CRS interference information may be CRS configurationinformation of the neighbor cell. For example, the CRS interferenceinformation includes a scrambling code ID, the number of CRS ports, andMBSFN subframe configuration information. Based on the CRS interferenceinformation of the neighbor cell, the CRS interference in which theneighbor cell is given to the serving cell may be removed. A detailedmethod of removing the CRS interference will be described below.

In addition, the PDSCH interference information includes a power ratioof the CRS to the PDSCH (alternatively, PB and/or PA), and probability(possibility) information of a modulation scheme. The power ratio of theCRS to the PDSCH and the probability (possibility) information of themodulation scheme are used for suppressing the PDSCH interference of theneighbor cell.

Hereinafter, the power ratio of the CRS to the PDSCH will be described.

The PDSCH and the CRS are transmitted by different power. Based on theinformation on the power, the UE may estimate whether the interferencefrom the PDSCH of a specific cell is received by some power(alternatively, some ratio). Accordingly, the UE may more exactlysuppress the interference. A detailed method of removing the PDSCHinterference will be described below.

Further, in the transmission based on a demodulation reference signal(DMRS), the power of the DMRS is the same as the power of the PDSCH in16QAM and 64QAM modulation. In the QPSK, since the power of the DMRS maybe different from the power of the PDSCH, the power ratio of the DMRS tothe PDSCH in the QPSK may be estimated based on information illustratedin Table 6.

Hereinafter, the probability (possibility) of the modulation scheme willbe described.

In order to suppress the inference by a minimum mean square error (MMSE)receiver, information on correlation values is very important. Thecorrelation values in different modulation schemes are different fromeach other. Since the scheduling by the eNB is dynamically performed,exactly reconfiguring the modulation scheme by the RRC in each subbandis impossible. Further, it is very difficult to exchange dynamicscheduling information between the eNBs by the non-ideal backhaul.However, the eNB may predict probability of each modulation scheme for arelatively long period based on the CSI feedback of all the UEs.Accordingly, performance of the MMSE IRC may be improved. A detailedmethod will be described below. The following Table 3 illustrates anexample for probability of different modulation schemes when all theresources are scheduled to the UE in the neighbor cell.

TABLE 3 Modulation scheme Probability QPSK 0.3 16QAM 0.4 64QAM 0.3

Referring to Table 3, probability that the QPSK is applied to thespecific UE is 0.3, probability that the 16QAM is applied is 0.4, andprobability that the 64QAM is applied is 0.3. The sum of theprobabilities may be the same as 1 or smaller than 1.

When an NAICS is increased by the semistatic scheduling in the network,interference factors such as the modulation will end a static state. Thescheme may automatically support this case. In this case, a probabilityvalue of different modulation schemes except form one modulation schemeis 0. For example, when one UE has a PDSCH of the neighbor cell by the16QAM in the RRC information by the semistatic scheduling, theprobability of the 16QAM is 1 and the probability of the QPSK and the64QAM is 0. The following Table 4 illustrates such an example.

TABLE 4 Modulation scheme Probability QPSK 0 16QAM 1 64QAM 0

Meanwhile, when information of Table 2 is illustrated as RRC signaling,the information is illustrated in Table 5 given below.

NAICS-Config-r12 ::=    SEQUENCE {     NeighCellsCRS-Info-r11 ::= CHOICE{      release        NULL,      setup CRS-AssistanceInfoList-r11 }CRS-AssistanceInfoList-r12 ::= SEQUENCE(SIZE (1..maxCellReport)) OF CRS- AssistanceInfo-r11CRS-AssistanceInfo-r12 ::= SEQUENCE {     physCellId-r12 PhysCellId,    antennaPortsCount-r12 ENUMERATED {an1, an2, an4, spare1},    mbsfn-SubframeConfigList-r12 MBSFN-SubframeConfigList,     ... }NeighCellsPDSCH-Info-r12 ::= CHOICE {      release NULL,      setupPDSCH-AssistanceInfoList-r12 } PDSCH-AssistanceInfo-r12 ::= SEQUENCE {    p-b INTEGER (0..3)     p-a ENUMERATED { dB-6, dB-4dot77, dB-3,dB-1dot77, dB0, dB1, dB2, dB3},     Probability-QPSK-r12ENUMERATED  {0,  0.1,  0.2,  0.3, 0.4,0.5,0.6,0.7,0.8,0.9,1},    Probability-16QAM-r12 ENUMERATED  {0,  0.1,  0.2,  0.3,0.4,0.5,0.6,0.7,0.8,0.9,1},     Probability-64QAM-r12ENUMERATED  {0,  0.1,  0.2,  0.3, 0.4,0.5,0.6,0.7,0.8,0.9,1},     ... }    ... }

Referring to Table 5, the RRC signaling largely includesCRS-AssistanceInfoList-r12 and PDSCH-AssistanceInfo-r12. Here, theCRS-AssistanceInfoList-r12 represents the CRS interference information,and the PDSCH-AssistanceInfo-r12 represents the PDSCH interferenceinformation.

First, the CRS-AssistanceInfoList-r12 includes physCellId-r12,antennaPortsCount-r12, and mbsfn-SubframeConfigList-r12. AphysCellId-r12 scrambling code ID has an integer value in the range of[0,503]. The number of antennaPortsCount-r12 CRS ports has an integervalue of 1, 2, or 4. The mbsfn-SubframeConfigList-r12 represents theMBSFN subframe configuration.

Further, the PDSCH-AssistanceInfo-r12 includes p-a and p-b (power ratiosPA and PB of the CRS to the PDSCH), and Probability-QPSK-r12,Probability-16QAM-r12, and Probability-64QAM-r12. TheProbability-QPSK-r12 represents probability to be modulated to the QPSKfrom the PDSCH of the neighbor cell, and a value thereof may have 0and 1. The Probability-16QAM-r12 represents probability to be modulatedto the 16QAM from the PDSCH of the neighbor cell, and a value thereofmay have 0 and 1. Further, the Probability-64QAM-r12 representsprobability to be modulated to the 64QAM from the PDSCH of the neighborcell, and a value thereof may have 0 and 1.

The embodiment may be applied to another channel as well as the PDSCH.In the detection of the ePDCCH, since the ePDCCH is allocated to thePDSCH region, the ePDCCH is placed in the same interference as thePDSCH. Accordingly, the ePDCCH may also use the information as it is.

According to another embodiment of the present invention, theinterference in the ePDCCH may be removed.

In more detail, the interference information of the ePDCCH may includean ePDCCH region, a power ratio of the CRS to the ePDCCH, andinformation of QPSK probability (possibility) in the ePDCCH. In the caseof the ePDCCH, even though the ePDCCH of the neighbor cell is allocatedin the PDCCH region, the modulation scheme is only the QPSK, and sincethe ePDCCH region is semistatically configured by the RRC signaling, theePDCCH is also static. Accordingly, when the information is set to theUE, the UE may suppress the interference from the ePDCCH. Further, sincethe power of the ePDCCH may be increased, the power ratio of the ePDCCHmay be included in the RRC signaling.

According to yet another embodiment of the present invention, theinterference in the PDCCH may also be removed.

In the case of the PDCCH, since the control region exits, the PDCCH isplaced in interference different from the PDSCH. If all the cells havethe same control region, the interference of the PDCCH exists only inthe QPSK. However, since the control region is not completely used atall times, the probability of the QPSK in the control region may beincluded in the RRC signaling. Like the ePDCCH, since the power of thePDCCH may be increased, the power ratio of the PDCCH may be included inthe RRC signaling.

The information on the ePDCCH and the PDCCH in all the interferencechannels for the NAICS may be included in a parameter set of thefollowing Table 6.

TABLE 6 Parameter set Information content CRS interference Scramblingcode ID information Integer value in range of [0, 503] Number of CRSports Integer value of 1, 2, or 4 MBSFN subframe configuration PDSCHPower ratio of CRS to PDSCH interference PB and PA informationProbability (possibility) of modulation scheme PDCCH Power ratio of CRSto PDCCH interference QPSK probability (possibility) in PDCCHinformation ePDCCH ePDCCH region (resource) interference Power ratio ofCRS to ePDCCH information QPSK probability (possibility) in ePDCCH DMRSinterference Power ratio of CRS to DMRS information

When a parameter set of Table 6 is represented by the RRC signaling, theparameter set is illustrated in Table 7.

NAICS-Config-r12 ::= SEQUENCE {     NeighCellsCRS-Info-r11 ::=    CHOICE{     release NULL,     setup    CRS-AssistanceInfoList-r11 }CRS-AssistanceInfoList-r12 ::= SEQUENCE  (SIZE  (1..maxCellReport))  OF CRS- AssistanceInfo-r11 CRS-AssistanceInfo-r12 ::= SEQUENCE {   physCellId-r12    PhysCellId,    antennaPortsCount-r12    ENUMERATED{an1, an2, an4, spare1},    mbsfn-SubframeConfigList-r12   MBSFN-SubframeConfigList,    ... } NeighCellsPDSCH-Info-r12 ::=CHOICE {     release NULL,     setup    PDSCH-AssistanceInfoList-r12 }PDSCH-AssistanceInfo-r12 ::= SEQUENCE {    p-b       INTEGER (0..3)   p-a       ENUMERATED {       dB-6, dB-4dot77, dB-3, dB-1dot77,      dB0, dB1, dB2, dB3},    Prability-QPSK-r12 ENUMERATED   {0,   0.1,  0.2,   0.3, 0.4,0.5,0.6,0.7,0.8,0.9,1}, Prability-16QAM-r12 ENUMERATED  {0,   0.1,   0.2,   0.3, 0.4,0.5,0.6,0.7,0.8,0.9,1},   Prability-64QAM-r12 ENUMERATED   {0,   0.1,   0.2,   0.3,0.4,0.5,0.6,0.7,0.8,0.9,1},    ... } PDCCH-AssistanceInfo-r12 ::=SEQUENCE {    p-b    INTEGER (0..3)    p-a    ENUMERATED {    dB-6,dB-4dot77, dB-3, dB-1dot77,    dB0, dB1, dB2, dB3},   Prability-QPSK-r12 ENUMERATED   {0,   0.1,   0.2,   0.3,0.4,0.5,0.6,0.7,0.8,0.9,1},     } ePDCCH-AssistanceInfo-r12 ::= SEQUENCE{    p-b    INTEGER (0..3)    p-a    ENUMERATED {    dB-6, dB-4dot77,dB-3, dB-1dot77,    dB0, dB1, dB2, dB3},    Prability-QPSK-r12ENUMERATED   {0,   0.1,   0.2,   0.3, 0.4,0.5,0.6,0.7,0.8,0.9,1},EPDCCH-SetConfig-r11 ::= SEQUENCE {    setConfigId-r11      EPDCCH-SetConfigId-r11,    transmissionType-r11    ENUMERATED{localised, distributed},    resourceBlockAssignment-r11    SEQUENCE{      numberPRB-Pairs-r11          ENUMERATED {n2, n4, n8},      resourceBlockAssignment-r11     BIT STRING (SIZE(4..38))    },   dmrs-ScramblingSequenceInt-r11    INTEGER (0..503),   pucch-ResourceStartOffset-r11  INTEGER (0..2047),   re-MappingQCL-ConfigId-r11    PDSCH-RE-MappingQCL-ConfigId-r11   OPTIONAL, -- Need OR    ... }     } DMRS-AssistanceInfo-r12 ::=SEQUENCE {    p-b    INTEGER (0..3)    p-a    ENUMERATED {    dB-6,dB-4dot77, dB-3, dB-1dot77,    dB0, dB1, dB2, dB3}, } ... }

Here, CRS-AssistanceInfoList-r12 represents CRS interferenceinformation, PDSCH-AssistanceInfo-r12 represent PDSCH interferenceinformation, ePDCCH-AssistanceInfo-r12 represents ePDCCH interferenceinformation, and DMRS-AssistanceInfo-r12 represents DMRS interferenceinformation.

First, the CRS-AssistanceInfoList-r12 includes physCellId-r12,antennaPortsCount-r12, and mbsfn-SubframeConfigList-r12. AphysCellId-r12 scrambling code ID has an integer value in the range of[0,503]. The number of antennaPortsCount-r12 CRS ports has an integervalue of 1, 2, or 4. The mbsfn-SubframeConfigList-r12 represents theMBSFN subframe configuration.

Further, the PDSCH-AssistanceInfo-r12 includes p-a and p-b (power ratiosPA and PB of the CRS to the PDSCH), and Probability-QPSK-r12,Probability-16QAM-r12, and Probability-64QAM-r12. TheProbability-QPSK-r12 represents probability to be modulated to the QPSKfrom the PDSCH of the neighbor cell, and a value thereof may have 0and 1. The Probability-16QAM-r12 represents probability to be modulatedto the 16QAM from the PDSCH of the neighbor cell, and a value thereofmay have 0 and 1. Further, the Probability-64QAM-r12 representsprobability to be modulated to the 64QAM from the PDSCH of the neighborcell, and a value thereof may have 0 and 1.

The PDCCH-AssistanceInfo-r12 includes p-a and p-b (power ratios PA andPB of the CRS to the PDCCH), and Probability-QPSK-r12,Probability-16QAM-r12, and Probability-64QAM-r12. TheProbability-QPSK-r12 represents probability to be modulated to the QPSKfrom the PDCCH of the neighbor cell, and a value thereof may have 0and 1. Since the PDCCH is modulated to only the QPSK, information onprobability to be modulated to the 16QAM or the 64QAM needs not to beused.

The ePDCCH-AssistanceInfo-r12 includes p-a and p-b (power ratios PA andPB of the CRS to the PDCCH), and Probability-QPSK-r12. TheProbability-QPSK-r12 represents probability to be modulated to the QPSKfrom the PDCCH of the neighbor cell, and a value thereof may have 0and 1. Since the ePDCCH is modulated to only the QPSK, information onprobability to be modulated to the 16QAM or the 64QAM needs not to beused.

The DMRS-AssistanceInfo-r12 includes p-a and p-b (power ratios PA and PBof the CRS to the PDCCH).

2. Removing Interference in Environment where CoMP is Applied

The CoMP has been supported by a scheme of avoiding interference betweencells through coordination for the current system. In order to support ahomogeneous network by some used schemes, an eNB having higher or lowertransmission power has been proposed. Different eNBs may have the sameor different cell IDs.

The CoMP scheme includes three types. A first scheme is jointtransmission in which a plurality of cells including a serving cellsimultaneously transmits PDSCHs, and the second scheme is a dynamicpoint selection (DPS). In this scheme, only one eNB transmits the PDSCH.A third scheme is a CS/CB scheme, and even in this scheme, only one eNBtransmits the PDSCH. The eNB may be changed only in semi-static.

It is difficult to remove interference from the CRS in the CoMP. Thereason is that the CRS may not be blanked. In the CoMP, when differenteNBs have different IDs, serious interference from the CRS of theneighbor eNB may exist. In a small cell, the CRS interference is moreserious. However, according to the embodiment of the present invention,the CRS interference may be efficiently removed.

FIG. 5 illustrates an example of a situation where interference occursin an environment where the CoMP is applied. Referring to FIG. 5, in theenvironment where the CoMP is applied, the UE may RE-map only one CRS.When different eNBs have different cell IDs, interference from the CRSof the neighbor eNB may occur. The problem is more serious when thePDSCH of the neighbor eNB is blanked. TP1 and TP2 exist, and the TP2 isselected as PeNB of one UE by the DPS. In order to reduce theinterference, the PDSCH in the same PRB of the TP1 is blanked. However,the CRS existing in the PRB of the PRB may not be blanked. Accordingly,some REs in the PDSCH of the UE still have the interference from theTP1. When an MCS level is set in the case of no interference, some REsmay have the interference from the TP1, and in this case, the CQI may bemismatched. According to the embodiment of the present invention, theinterference due to the situation may be removed.

Generally, the interference from the CSI-RS of the neighbor cell is nota serious problem. The reason is that the PDSCH RE is muted by theZP-CSI-RS when the PDSCH RE is used for the CSI-RS of the neighbor cell.The interference from the CSI-RS may cause two problems below.

-   -   The eNB does not mute the PDSCH RE in order to reduce overhead        for the CSI-RS of the neighbor cell. Accordingly, the ZP-CSI-RS        of the serving cell does not overlap with the CSI-RS of the        neighbor cell.    -   In the case of the CoMP, a plurality of ZP-CSI-RSs may be        configured. In one subframe, in order to map the PDSCH RE, only        the ZP-CSI-RS of only one transmission eNB is selected. In the        DPS, when the transmission eNB is not the serving cell, some        CSI-RSs of the neighbor cell may not be muted. This causes the        CSI-RS interference.

FIG. 6 is a diagram illustrating one example of a situation in whichCSI-RS interference occurs under a CoMP environment.

Referring to FIG. 6, four eNBs exist, and each eNB corresponds to a TP.The CSI-RS and the ZP-CSI-RS defined by the first to fourth CSI-RSsCSI-RS1 to 4 and the first to fourth ZP-CSI-RSs ZP-CSI-RS1 to 4 areconfigured. The TP1, the TP2, and the TP3 are a CoMP set for one UE.Accordingly, the first to third CSI-RSs and the first to thirdZP-CSI-RSs may be configured with respect to the UE. In the DPS, whenthe TP2 is selected as the PeNB, the first to third CSI-RSs and thesecond ZP-CSI-RS may be considered for the PDSCH RE mapping. Since theTP4 is not the neighbor eNB of the TP2, the fourth CSI-RS is not coveredby the second ZP-CSI-RS. Accordingly, the fourth CSI-RS provides theinterference to the UE in this subframe.

When the CoMP is applied, the interference from the PDSCH of theneighbor cell may be muted through coordination, and the eNB providesthe CRS and CSI-RS interference information. Based on the information,the UE removes the interference by the improved receiver.

In order to remove the interference when the CoMP is applied, methodsproposed in the present invention are as follows.

1) Consider CRS interference information in CoMP operation.

2) Consider CRS interference information to be removed.

3) Transmit CRS and CSI-RS interference information addition to thePDSCH RE mapping information and the QCL information to the UE.

The eNB may configure four PDSCH rate matching per one component carrierand QCL sets. Each QCL set includes two information. One is the PDSCH REmapping information, and the other one is QCL information for one DMRS.

The following Table 8 illustrates a parameter set to be transmitted tothe UE in order to remove the interference of the CRS and the CSI-RSaccording to the present invention.

TABLE 8 Parameter set Information content PDSCH RE CRS patterninformation for PDSCH RE mapping mapping information PDSCH startingpoint ZP-CSI-RS for PDSCH RE mapping QCL information CSI-RS estimatingQCL for DMRS for DMRS NAICS CRS information to be removed informationCSI-RS information to be removed PDSCH information to be removed

In order to indicate the CRS information for removing the interference,the eNB needs to notify a detailed order to the UE. The CRS informationfield to be indicated for the NAICS is illustrated in Table 9 below.

TABLE 9 Field Content n_(CRS)_ic Number of CRS ports One integer valueof 1, 2, and 4 Scrambling code ID Cell ID to remove CRS Integer value inrange of [0, 503] MBSFN subframe MBSFN subframe configurationconfiguration

The CSI-RS information field to be indicated for removing theinterference is illustrated in Table 10 below. A Pc value is notrequired because the Pc value is used for the CSI feedback.

TABLE 10 Field Content antennaPortsCount Number of antenna ports usedfor CSI-RS transmission (1, 2, 4, or 8). ResourceConfig CSI-RSconfiguration defined in TS 36.211., table 6.10.5.2-1 SubframeConfigI_(CSI-RS) defined in TS 36.211., table 6.10.5.3-1 N_(ID) ^(CSI) Virtualcell ID in initial state of CSI-RS scrambling and integer value in rangeof [0, 503]

A set of PDSCH RE mapping, QCL, and NAICS parameters indicated in eachcode point in the DCI format 2D is illustrated in Table 11 below.

TABLE 11 Field Content n_(CRS) Number of CRS ports 1, 2, 4, and integervalues including preliminary values which are not attached to Rel-11 UEform v_(shift) Position on frequency domain of CRS Integer in range of[0, 5] MBSFN MBSFN subframe configuration subframe configuration PDSCH-PDSCH-Start Symbol Start-Sym {0 or preliminary value (FFS), 1, 2, 3, and4 (4 may be applied only when system BW <=10PRB) as value indicated byPCFICH of serving cell in the case of non-cross-carrier-scheduling orvalue set in upper layer in the case of cross-carrier-schedulingzeroTxPower zeroTxPowerResourceConfigList, and ZP CSI-RS set CSI-RSvalue determined by zeroTxPowerSubframeConfig and assumed by PDSCH ratematching and RE mapping of UE QuasiCo Non-zero power CSI-RS resourceindex indicated by Location- quasi-colocatgion assumption on DMRS IndexNumber of CRS ports for removing interference n_(CRS)_ic One integervalue of 1, 2, and 4 cellID Cell ID for CRS to be removed MBSFN MBSFNsubframe configuration subframe configuration antennaPorts Number ofantenna ports used for CSI-RS to be Count removed (1, 2, 4, or 8).ResourceConfig CSI-RS configuration to be removed SubframeConfigI_(CSI-RS) N_(ID) ^(CSI) Virtual cell ID in initial state of CSI-RSscrambling and integer value in range of [0, 503]

Referring to Table 11, only one CRS and one CSI-RS are used for theNAICS, but a plurality of CRSs and CSI-RSs may be used.

Further, the ePDCCH may be used for supporting RE mapping, QCL, andCRS/CSI-RS interference removal.

The PDSCH RE mapping, QCL, and radio resource control (RRC) signalingfor the NAICS are shown in Table 12.

TABLE 12 RE-MappingQCLNAICSConfigToAddModList-r12 ::= SEQUENCE    (SIZE(1..maxRE-MapQCL-r11)) OF PDSCH-RE-MappingQCL-Config-r11RE-MappingQCLNAICSConfigToReleaseList-r12 ::= SEQUENCE  (SIZE (1..maxRE- MapQCL-r11)) OF PDSCH-RE-MappingQCLNAICS-ConfigId-r12PDSCH-RE-MappingQCLNAICS-Config-r12 ::= SEQUENCE {   pdsch-RE-MappingQCLNAICS-ConfigId-r12 PDSCH-RE-MappingQCLNAICS-ConfigId-r12,    optionalSetOfFields-r12 SEQUENCE {      crs-PortsCount-r11 ENUMERATED {n1, n2, n4, spare1},      crs-FreqShift-r11 INTEGER (0..5),      mbsfn-SubframeConfigList-r11 CHOICE {          release NULL,         setup SEQUENCE {             subframeConfigList MBSFN-SubframeConfigList          }       } OPTIONAL,  --  Need ON      pdsch-Start-r11 ENUMERATED {reserved, n1, n2, n3, n4, assigned}   } OPTIONAL, -- Need OP    csi-RS-ConfigZPId-r11CSI-RS-ConfigZPId-r11,    qcl-CSI-RS-ConfigNZPId-r11CSI-RS-ConfigNZPId-r11       OPTIONAL,  -- NeighCellsCRS-Info-r11 ::=CHOICE {    release NULL,    setup CRS-AssistanceInfoList-r11 }CRS-AssistanceInfoList-r12 ::= SEQUENCE  (SIZE  (1..maxCellReport))  OF CRS- AssistanceInfo-r11 CRS-AssistanceInfo-r12 ::= SEQUENCE {   physCellId-r12 PhysCellId,    antennaPortsCount-r12 ENUMERATED {an1,an2, an4, spare1},    mbsfn-SubframeConfigList-r12MBSFN-SubframeConfigList,    ... } NeighCellsCSI-RS-Info-r12 ::= CHOICE{    release NULL,    setup CSI-RS-AssistanceInfoList-r12 }CSI-RS-AssistanceInfoList-r12 ::= SEQUENCE (SIZE (1..maxCellReport)) OFCSI- RS-AssistanceInfo-r12 CSI-RS-AssistanceInfo-r12 ::= SEQUENCE {   antennaPortsCount-r11 ENUMERATED {an1, an2, an4, an8},   resourceConfig-r11 INTEGER (0..31),    subframeConfig-r11 INTEGER(0..154),    scramblingIdentity-r11 INTEGER (0..503),    ... } Need OR   ... qcl-CRS-Info-r11 SEQUENCE {       qcl-ScramblingIdentity-r11INTEGER (0..503),       crs-PortsCount-r11 ENUMERATED {n1, n2, n4,spare1},       mbsfn-SubframeConfigList-r11 CHOICE {             releaseNULL,             setup SEQUENCE {                subframeConfigListMBSFN- SubframeConfigList             }

3. Interference Removing and Suppressing Method at Receiver Side

A receiver (in particular, UE) that receives CRS, PDSCH, PDCCH, ePDCCH,and the like may acquire a parameter aggregation based on the RRCsignaling and remove or suppress the interference by using the parameteraggregation. The removal or suppression of the interference may beperformed according to the following procedure.

First, a received signal without interference by the PDSCH, CSI-RS, andCRS received by the UE from a specific neighbor cell may be expressed byEquation 1 given below.Y=H _(i) X _(i) +I  [Equation 1]

In the equation, H_(i) represents a channel of the PDSCH transmitted tothe UE from the PeNB. X_(i) represents a PDSCH data symbol. I representsadditive white Gaussian noise (AWGN) and other inter-cell interferencewhich are not considered in the present invention.

A received signal with interference by the CSI-RS and the CRS receivedby the UE may be expressed by Equation 2 given below.Y=H _(i) X _(i) +H _(j) S _(j) +I  [Equation 2]H_(j) is a channel from not the PeNB but other eNB. However, thistransmits the CRS or the CSI-RS that gives interference. S_(j)represents a sequence symbol of the CRS or the CSI-RS.

The UE may estimate S_(j) without performing the detection based on theRRC signaling provided in the present invention.

When it is assumed that the estimated H_(j) is Ĥ_(j), the interferencemay be removed by the following method.{tilde over (Y)}=Y−Ĥ _(j) S _(j) =H _(i) X _(i)+(H _(j) −Ĥ _(j))S _(j)+I  [Equation 3]

If performance of estimating Hj is high, that is, if Ĥ_(j)≈H_(j), theinterference from the CRS or the CSI-RS may be removed. Accordingly, allPDSCH symbols have similar performance regardless the CRS or CRI-RSinterference.

The PDSCH interference from the neighbor cell received by the UE may beexpressed as Equation 4 given below.Y=H _(i) X _(i) +H _(j) X _(j) +I  [Equation 2]

In the equation, X_(j) represents the PDSCH symbol of the neighbor cell.

The UE may acquire a data symbol given below by a linear receiver.{circumflex over (X)} _(i) =WY  [Equation 5]W=({tilde over (H)} _(i) ^(H) {tilde over (H)} _(i) +R _(P) +R _(I))⁻¹{tilde over (H)} _(i) ^(H)  [Equation 6]

In the equation, R_(P) and R_(I) are correlation values of the PDSCHinterference and other interference.R _(P) =E{(H _(j) X _(j))(H _(j) X _(j))^(H) }=E(H _(j) X _(j) X _(j)^(H) H _(j) ^(H))=H _(j) E(X _(j) X _(j) ^(H))H _(j) ^(H)  [Equation 7]

R_(f) as a sum of weak inter-cell interference and AWGNs may begenerally assumed as the AWGN. Accordingly, the AWGN may not besuppressed and in the present invention, the AWGN value is notconsidered. H_(j) may be estimated by the CRS or DMRS. If H_(j) isestimated as {tilde over (H)}_(j) by the CRS, a power ratio of the PDSCHto the CRS is required. Herein, the ratio value is assumed as ρ.

A value of E(X_(j)X_(j) ^(H)) varies depending on a modulation scheme.E(X_(j)H_(j) ^(H)) in QPSK, 16QAM, and 64QAM is defined as R_(QPSK),R_(16QAM), and R_(64QAM).

When it is assumed that probabilities of the modulation schemes QPSK,16QAM, and 64QAM are P_(QPSK), P_(16QAM), and P_(64QAM), respectively,the values of E(X_(j)X_(j) ^(H)) and R_(P) are shown in Equations 8 and9 given below.E(X _(j) X _(j) ^(H))=P _(QPSK) R _(QPSK) +P _(16QAM) R _(16QAM) +P_(64QAM) R _(64QAM)  [Equation 8]R _(P) =ρ{tilde over (H)} _(j)(P _(QPSK) R _(QPSK) +P _(16QAM) R_(16QAM) +P _(64QAM) R _(64QAM)){tilde over (H)} _(j) ^(H)  [Equation 9]

An MMSE-IRC receiver may more efficiently suppress the PDSCHinterference from the neighbor cell by the R_(P).

FIG. 7 is a flowchart illustrating an operating sequence of a UE forremoving inter-cell interferences according to the present invention.

Referring to FIG. 7, first, the UE receives RRC signaling includinginformation on interference which the CRS and the PDSCH of the neighborcell may give to the UE and a serving cell in which a communication linkis configured (S710). The RRC signaling is received from the servingcell. The information on the CRS interference includes the scramblingcode ID, the number of CRS ports, and the MBSFN subframe configuration.The scrambling code ID has an integer value in the range of 0 to 503 andthe number of CRS ports has an integer value of 1, 2, or 4.

The RRC signal may include information on the interference which thePDSCH of the neighbor cell may give to the PDSCH of the serving cell.The information on the PDSCH interference includes the power ratio ofthe PDSCH and the CRS and a probability of the modulation scheme. Themodulation scheme may include QPSK, 16QAM, and 64QAM and the probabilityof the modulation scheme represents probabilities to be modulated by therespective schemes QPSK, 16QAM, and 64QAM.

Next, the UE receives the PDSCH of the serving cell including theinterference of the neighbor cell (S270). For example, the PDSCH mayinclude the interferences by the CRS and the PDSCH of the neighbor cell.

The UE that receives the PDSCH may blind-detect the PDCCH or the ePDCCHin order to acquire an approval for a downlink (DL). The blind-detectionmay be performed by known technology.

Next, the UE calculates a channel estimation value in the serving cell(S730). The channel estimation value is calculated based on interferenceincluded in the CRS, PDSCH, and RRC signaling including theinterference. As an embodiment, the UE first acquires a first channelestimation value by using the CRS of the serving cell and derives asecond channel estimation value in which the interference of theneighbor cell is removed from the first channel estimation value. Inthis example, the channel estimation value is acquired stepwise, butaccording to another embodiment, the UE may immediately calculate thechannel estimation value of the serving cell by considering theinterference of the neighbor cell.

A detailed calculation method is described in Equations 1 to 9 and adescription thereof. Equations 1 to 3 and a description of the equationsrelate to a method for removing the CRS interference. Further, Equations1 to 3 and a description of the equations relate to a method forremoving the PDSCH interference by the neighbor cell. The PDSCHinterference may be suppressed by calculating an MMSE detection weight.The MMSE detection weight may be calculated by Equations 4 to 7 and adescription of the equations. Since only the interference in the CRS andthe CSI-RS is considered under an environment to which CoMP is applied,a process of removing the PDSCH interference by the interference cell bycalculating the MMSE detection weight may be omitted.

Last, the UE performs communication in the serving cell (S740). As theinterferences by the CRS and the PDSCH of the neighbor cell are removedand suppressed, the performance of the communication is furtherimproved.

In other words, the UE receives the PDSCH through the first serving cell(the serving cell); and performs a channel estimation for retrievingdata from a PDSCH of the first serving cell, the channel estimationcomprising: performing a first channel estimation for the PDSCH of thefirst serving cell based on a CRS of the first serving cell, based oninterference information of the CRS of the neighbor cell, canceling aninterference of the CRS of the neighbor cell from the first channelestimation, and based on the parameter relating to the power ratio ofthe CRS of the neighbor cell and the PDSCH of the neighbor cell,performing a second channel estimation for the PDSCH of the firstserving cell by canceling an interference of the PDSCH of the neighborcell; and perform to retrieve the data from the PDSCH of the firstserving cell based on the second channel estimation. Herein the UEtransmits capability information to the base station through the firstserving cell via a UE capability information procedure, the UEcapability information procedure includes that the capabilityinformation indicating that the UE is capable of receiving networkassisted interference cancellation and suppression (NAICS) information,wherein the NAICS information is used by the UE to cancel and/or tosuppress at least one of an intra-cell interference and an inter-cellinterference. In this embodiments, the UE receives the RRC signal ofNAICS information (including cancellation information of CRS of theneighbor cell and the PDSCH of the neighbor cell) for the serving cell,wherein the RRC message comprises a NAICS_Config message, theNAICS_Config message comprising a CRS-AssistanceInfo field having theCRS information of the neighbor cell and a PDSCH-AssistanceInfo fieldhaving the PDSCH information of the neighbor cell, wherein thePDSCH-AssistanceInfo field comprises a field for the first powerparameter (p-a) and a field for the second power parameter (p-b), andwherein the field for the second power parameter (p-b) comprises atleast one of 0, 1, 2, and 3, and the field for the first power parameter(p-a) comprises at least one of dB-6, dB-4dot77, dB-3, dB-1dot77, dB0,dB1, dB2, and dB3.

FIG. 8 is a flowchart of data for removing the inter-cell interferencesaccording to the present invention; and

Referring to FIG. 8, the eNB transmits to the UE the RRC signalingincluding information on the interference which the CRS and the PDSCH ofthe neighbor cell may give to the serving cell (S810). The informationon the CRS interference includes the scrambling code ID, the number ofCRS ports, and the MBSFN subframe configuration. The scrambling code IDhas an integer value in the range of 0 to 503 and the number of CRSports has an integer value of 1, 2, or 4. The RRC signal may includeinformation on the interference which the PDSCH of the neighbor cell maygive to the PDSCH of the serving cell. The information on the PDSCHinterference includes the power ratio of the PDSCH and the CRS and aprobability of the modulation scheme. The modulation scheme may includeQPSK, 16QAM, and 64QAM and the probability of the modulation schemerepresents probabilities to be modulated by the respective schemes QPSK,16QAM, and 64QAM.

Next, the eNB transmits to the UE the CRS and the PDSCH of the servicecell including the interference of the neighbor cell (S820). The CRS andthe PDSCH may include the interferences by the CRS and the PDSCH of theneighbor cell.

Next, the UE calculates a channel estimation value in the serving cell(S830). The channel estimation value is calculated based on interferenceincluded in the CRS, PDSCH, and RRC signaling including theinterference. As an embodiment, the UE first acquires a first channelestimation value by using the CRS of the serving cell and derives asecond channel estimation value in which the interference of theneighbor cell is removed from the first channel estimation value. Inthis example, the channel estimation value is acquired stepwise, butaccording to another embodiment, the UE may immediately calculate thechannel estimation value of the serving cell by considering theinterference of the neighbor cell.

A detailed calculation method is described in Equations 1 to 9 and adescription thereof. Equations 1 to 3 and the description of theequations relate to the method for removing the CRS interference and inparticular, to a method for removing the interference (hereinafter, theinterference in the PDSCH) which the CRS of the neighbor cell gives tothe PDSCH of the serving cell. The PDSCH interference may be suppressedby calculating the MMSE detection weight. The MMSE detection weight maybe calculated by Equations 4 to 7 and a description of the equations.Since only the interference in the CRS and the CSI-RS is consideredunder an environment to which CoMP is applied, a process of removing thePDSCH interference by the interference cell by calculating the MMSEdetection weight may be omitted.

Last, the UE performs communication in the serving cell (S840). As theinterferences by the CRS and the PDSCH of the neighbor cell are removedand suppressed, the performance of the communication is furtherimproved.

FIG. 9 is a block diagram illustrating a UE and an eNB according to oneexample of the present invention.

Referring to FIG. 9, the UE 900 includes a receiving unit 905, a channelestimating unit 910, and a transmitting unit 915.

The receiving unit 905 receives RRC signaling including information oninterference from an eNB 950, and at least one of a CRS, a PDSCH, aPDCCH, an ePDCCH, and a DMRS of a serving cell. The receiving unit 905receives at least one of the CRS, the PDSCH, the PDCCH, the ePDCCH, andthe DMRS of the serving cell to interfere from the neighbor cell.

Information on the CRS interference includes a scrambling code ID, thenumber of CRS ports, and an MBSFN subframe configuration as illustratedin Table 2. The scrambling code ID has an integer value in a range of 0to 503, and the number of CRS ports has an integer value of 1, 2, or 4.Information on the interference in the PDSCH of the serving cell fromthe PDSCH of the neighbor cell may be included in the RRC signaling. Theinformation on the PDSCH interference includes a power ratio of the CRSto the PDSCH and probability (possibility) of a modulation scheme. Themodulation scheme may include QPSK, 16QAM, and 64QAM, and theprobability of the modulation scheme represents probability to bemodulated to each scheme of QPSK, 16QAM, and 64QAM.

The channel estimating unit 910 calculates a channel estimation value inthe serving cell. The channel estimation value is calculated based onthe CRS and the PDSCH in which the interference is included, and theinformation on interference included in the RRC signaling. As anexample, the channel estimating unit 910 first calculates a firstchannel estimation value by using the CRS of the serving cell, anddeducts a second channel estimation value acquired by removing theinterference of the neighbor cell from the first channel estimationvalue. In the example, it is described that the channel estimationvalues are calculated by stages, but according to another embodiment,the channel estimating unit 910 may immediately calculate channelestimation values of the serving cell by considering the interference ofthe neighbor cell.

The channel estimating unit 910 may perform channel estimation based onEquations 1 to 9. Equations 1 to 3 and the description of Equationsrelate to the method of removing the CRS interference, and moreparticularly, to the method of removing the interference in the PDSCH ofthe serving cell from the CRS of the neighbor cell. The interference inthe PDSCH may be suppressed by calculating an MMSE detection weightedvalue. The MMSE detection weighted value may be calculated by Equations4 to 7 and the description of Equations. Under the environment where theCoMP is applied, since only the interference in the CRS and the CSI-RSis considered, a process of removing the PDSCH interference from theneighbor cell by calculating the MMSE detection weighted value may beomitted.

The transmitting unit 915 transmits an uplink signal to the eNB 950 inthe serving cell based on the channel estimation value. As the aboveinterference from the CRS and the PDSCH of the neighbor cell is removedor suppressed, the performance of communication is more improved.

The eNB 950 includes a transmitting unit 955, a receiving unit 960, areference signal generating unit 971, and an RRC control unit 972.

Here, the eNB 950 provides the serving cell, and transmits the CRS ofthe serving cell to the UE 900. The interference from the CRS and thePDSCH of the neighbor cell may be included in the CRS and the PDSCH ofthe neighbor cell.

The transmitting unit 955 transmits the CRS generated in the referencesignal generating unit 971, the DMRS, and the RRC signaling generated inthe RRC control unit 972 to the UE.

The receiving unit 960 receives an uplink signal transmitted from thetransmitting unit 915 of the UE 900.

The reference signal generating unit 971 generates reference signalssuch as the CRS and the DMRS to transmit the generated reference signalsto the transmitting unit 955.

The RRC control unit 972 generates RRC signaling including informationon the interference in the serving cell from the CRS and the PDSCH ofthe neighbor cell to transmit the generated RRC signaling to thetransmitting unit 955.

The UE 900 may establish a Radio Resource Control (RRC) connection withan eNB 950 through a serving cell (e.g., a primary serving cell) andreceive an RRC message through the serving cell. The RRC messageincludes cell-specific reference signal (CRS) information of a neighborcell and Physical Downlink Shared Channel (PDSCH) information of theneighbor cell, and the PDSCH information of the neighbor cell includes aparameter relating to a power ratio of a CRS of the neighbor cell and aPDSCH of the neighbor cell. The UE 900 receives the PDSCH through theserving cell and performs a channel estimation for retrieving data froma PDSCH of the serving cell.

The channel estimation includes: performing a first channel estimationfor the PDSCH of the serving cell based on a CRS of the serving cell;based on interference information of the CRS of the neighbor cell,canceling an interference of the CRS of the neighbor cell from the firstchannel estimation; and based on the parameter relating to the powerratio of the CRS of the neighbor cell and the PDSCH of the neighborcell, performing a second channel estimation for the PDSCH of theserving cell by canceling an interference of the PDSCH of the neighborcell. The UE 900 retrieves the data from the PDSCH of the serving cellbased on the second channel estimation.

The UE 900 may transmit capability information to the eNB 950 through aprimary serving cell. The capability information may indicate that theUE 900 is capable of receiving NAICS information. The UE 900 may use theNAICS information to cancel and/or suppress at least one of anintra-cell interference and an inter-cell interference.

The capability information may be a piece of UE capability informationof the UE 900.

The CRS information of the neighbor cell includes a scrambling codeidentification for the neighbor cell, the number of CRS ports of theneighbor cell, and a configuration of Multicast-Broadcast SingleFrequency Network (MBSFN) subframe. The PDSCH information of theneighbor cell includes a first power parameter (p-a) and a second powerparameter (p-b).

The RRC message may further include a NAICS_Config message, and theNAICS_Config message includes a CRS-AssistanceInfo field having the CRSinformation of the neighbor cell and a PDSCH-AssistanceInfo field havingthe PDSCH information of the neighbor cell. The PDSCH-AssistanceInfofield includes a field for the first power parameter (p-a) and a fieldfor the second power parameter (p-b).

The field for the second power parameter (p-b) includes at least one of0, 1, 2, and 3, and the field for the first power parameter (p-a)includes at least one of dB-6, dB-4dot77, dB-3, dB-1dot77, dB0, dB1,dB2, and dB3.

The PDSCH information of the neighbor cell includes probabilityinformation of a modulation scheme for the PDSCH of the neighbor cell,and

the probability information includes probability information for a firstmodulation scheme and probability information of a second modulationscheme. The modulation schemes may be one of QPSK, 16QAM, and 64QAM.

the RRC message comprises CRS information of the first serving cell andPDSCH information of the first serving cell, and

The PDSCH information of the serving cell may include a parameterrelating to a power ratio of a CRS of the serving cell and a PDSCH ofthe serving cell.

The CRS information of the serving cell comprises a scrambling codeidentification of the first serving cell, the number of CRS ports forthe serving cell, and configuration of Multicast-Broadcast SingleFrequency Network (MBSFN) subframe. The PDSCH information of the servingcell includes a first power parameter (p-a) relating to the serving celland a second power parameter (p-b) relating to the serving cell.

A field for the second power parameter (p-b) relating to the servingcell includes at least one of 0, 1, 2, and 3, and a field for the firstpower parameter (p-a) relating to the serving cell includes at least oneof dB-6, dB-4dot77, dB-3, dB-1dot77, dB0, dB1, dB2, and dB3.

The RRC message further includes interference information of an enhancedPhysical Downlink Control Channel (ePDCCH) of the neighbor cell.

The interference information of the ePDCCH of the neighbor cell includesan ePDCCH region of the neighbor cell, a parameter relating to a powerratio of the CRS of the neighbor cell and the ePDCCH of the neighborcell, and probability information of quadrature phase shift keying(QPSK) used for the ePDCCH.

According to the present invention, the transmission performance of thePDSCH is more improved by removing the CRS interference and the CSI-RSinterference and suppressing the PDSCH interference.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.Thus, the present invention is not limited to the foregoing embodimentsand may include all the embodiments within the scope of the appendedclaims.

What is claimed is:
 1. A User Equipment (UE) to perform a wirelesscommunication in an inter-cell interference environment, the UEcomprising: a processor to establish a Radio Resource Control (RRC)connection with a base station through a first serving cell, and toperform a channel estimation for retrieving data from a PhysicalDownlink Shared Channel (PDSCH) of the first serving cell; and areceiver to receive an RRC message through the first serving cell, theRRC message comprising cell-specific reference signal (CRS) informationof a neighbor cell and PDSCH information of the neighbor cell, and thePDSCH information of the neighbor cell comprising a parameter relatingto a power ratio of a CRS of the neighbor cell and a PDSCH of theneighbor cell, and to receive the PDSCH through the first serving cell,wherein the channel estimation comprises: performing a first channelestimation for the PDSCH of the first serving cell based on a CRS of thefirst serving cell, based on interference information of the CRS of theneighbor cell, canceling an interference of the CRS of the neighbor cellfrom the first channel estimation, and based on the parameter relatingto the power ratio of the CRS of the neighbor cell and the PDSCH of theneighbor cell, performing a second channel estimation for the PDSCH ofthe first serving cell by canceling an interference of the PDSCH of theneighbor cell; and wherein the processor retrieves the data from thePDSCH of the first serving cell based on the second channel estimation.2. The UE of claim 1, further comprising: a transmitter to transmitfirst capability information to the base station through the firstserving cell, the capability information indicating that the UE iscapable of receiving network assisted interference cancelation andsuppression (NAICS) information, wherein the NAICS information is usedby the UE to cancel and/or to suppress at least one of an intra-cellinterference and an inter-cell interference.
 3. The UE of claim 2,wherein the first capability information is included in UE capabilityinformation of the UE.
 4. The UE of claim 1, wherein the CRS informationof the neighbor cell comprises a scrambling code identification for theneighbor cell, the number of CRS ports of the neighbor cell, and aconfiguration of Multicast-Broadcast Single Frequency Network (MBSFN)subframe, and wherein the PDSCH information of the neighbor cellcomprises a first power parameter (p-a) and a second power parameter(p-b).
 5. The UE of claim 4, wherein the RRC message comprises aNAICS_Config message, the NAICS_Config message comprising aCRS-AssistanecInfo field having the CRS information of the neighbor celland a PDSCH-AssistanceInfo field having the PDSCH information of theneighbor cell, wherein the PDSCH-AssistanceInfo field comprises a fieldfor the first power parameter (p-a) and a field for the second powerparameter (p-b), and wherein the field for the second power parameter(p-b) comprises at least one of 0, 1, 2, and 3, and the field for thefirst power parameter (p-a) comprises at least one of dB-6, dB-4dot77,dB-3, dB-1dot77, dB0, dB1, dB2, and dB3.
 6. The UE of claim 1, whereinthe PDSCH information of the neighbor cell comprises probabilityinformation of a modulation scheme for the PDSCH of the neighbor cell,and wherein the probability information comprises probabilityinformation for a first modulation scheme and probability information ofa second modulation scheme.
 7. The UE of claim 1, wherein the RRCmessage comprises CRS information of the first serving cell and PDSCHinformation of the first serving cell, and wherein the PDSCH informationof the first serving cell comprises a parameter relating to a powerratio of a CRS of the first serving cell and a PDSCH of the firstserving cell.
 8. The UE of claim 7, wherein the CRS information of thefirst serving cell comprises a scrambling code identification of thefirst serving cell, the number of CRS ports for the first serving cell,and configuration of Multicast-Broadcast Single Frequency Network(MBSFN) subframe, and wherein the PDSCH information of the first servingcell comprises a first power parameter (p-a) relating to the firstserving cell and a second power parameter (p-b) relating to the firstserving cell.
 9. The UE of claim 8, wherein a field for the second powerparameter (p-b) relating to the first serving cell comprises at leastone of 0, 1, 2, and 3, and a field for the first power parameter (p-a)relating to the first serving cell comprises at least one of dB-6,dB-4dot77, dB-3, dB-1dot77, dB0, dB1, dB2, and dB3.
 10. The UE of claim1, wherein the RRC message further comprises interference information ofan enhanced Physical Downlink Control Channel (ePDCCH) of the neighborcell, and wherein the interference information of the ePDCCH of theneighbor cell comprises an ePDCCH region of the neighbor cell, aparameter relating to a power ratio of the CRS of the neighbor cell andthe ePDCCH of the neighbor cell, and probability information ofquadrature phase shift keying (QPSK) used for the ePDCCH.
 11. A basestation to perform a wireless communication in an inter-cellinterference environment, the base station comprising: a processor toestablish a Radio Resource Control (RRC) connection with a UserEquipment (UE) through a first serving cell; and a transmitter totransmit, to the UE, an RRC message through the first serving cell, theRRC message comprising cell-specific reference signal (CRS) informationof a neighbor cell and Physical Downlink Shared Channel (PDSCH)information of the neighbor cell, and the PDSCH information of theneighbor cell comprising a parameter relating to a power ratio of a CRSof the neighbor cell and a PDSCH of the neighbor cell, and to transmitthe PDSCH through the first serving cell, wherein the parameter relatingto the power ratio of the CRS of the neighbor cell and the PDSCH of theneighbor cell is configured for the UE to cancel an interference of thePDSCH of the neighbor cell in retrieving data from the PDSCH of thefirst serving cell, wherein the RRC message further comprisesinterference information of an enhanced Physical Downlink ControlChannel (ePDCCH) of the neighbor cell, and wherein the interferenceinformation of the ePDCCH of the neighbor cell comprises an ePDCCHregion of the neighbor cell, a parameter relating to a power ratio ofthe CRS of the neighbor cell and the ePDCCH of the neighbor cell, andprobability information of quadrature phase shift keying (QPSK) used forthe ePDCCH.
 12. The base station of claim 11, further comprising: areceiver to receive first capability information from the UE through thefirst serving cell, the capability information indicating that the UE iscapable of receiving network assisted interference cancelation andsuppression (NAICS) information, wherein the transmitter transmits theNAICS information for the UE to cancel and/or to suppress at least oneof an intra-cell interference and an inter-cell interference.
 13. Thebase station of claim 12, wherein the first capability information isincluded in UE capability information of the UE.
 14. The base station ofclaim 11, wherein the CRS information of the neighbor cell comprises ascrambling code identification for the neighbor cell, the number of CRSports of the neighbor cell, and a configuration of Multicast-BroadcastSingle Frequency Network (MBSFN) subframe, and wherein the PDSCHinformation of the neighbor cell comprises a first power parameter (p-a)and a second power parameter (p-b).
 15. The base station of claim 14,wherein the RRC message comprises a NAICS_Config message, theNAICS_Config message comprising a CRS-AssistanecInfo field having theCRS information of the neighbor cell and a PDSCH-AssistanceInfo fieldhaving the PDSCH information of the neighbor cell, wherein thePDSCH-AssistanceInfo field comprises a field for the first powerparameter (p-a) and a field for the second power parameter (p-b), andwherein the field for the second power parameter (p-b) comprises atleast one of 0, 1, 2, and 3, and the field for the first power parameter(p-a) comprises at least one of dB-6, dB-4dot77, dB-3, dB-1dot77, dB0,dB1, dB2, and dB3.
 16. The base station of claim 11, wherein the PDSCHinformation of the neighbor cell comprises probability information of amodulation scheme for the PDSCH of the neighbor cell, and wherein theprobability information comprises probability information for a firstmodulation scheme and probability information of a second modulationscheme.
 17. The base station of claim 11, wherein the RRC messagecomprises CRS information of the first serving cell and PDSCHinformation of the first serving cell, and wherein the PDSCH informationof the first serving cell comprises a parameter relating to a powerratio of a CRS of the first serving cell and a PDSCH of the firstserving cell.
 18. The base station of claim 17, wherein the CRSinformation of the first serving cell comprises a scrambling codeidentification of the first serving cell, the number of CRS ports forthe first serving cell, and configuration of Multicast-Broadcast SingleFrequency Network (MBSFN) subframe, and wherein the PDSCH information ofthe first serving cell comprises a first power parameter (p-a) relatingto the first serving cell and a second power parameter (p-b) relating tothe first serving cell.
 19. The base station of claim 18, wherein afield for the second power parameter (p-b) relating to the first servingcell comprises at least one of 0, 1, 2, and 3, and a field for the firstpower parameter (p-a) relating to the first serving cell comprises atleast one of dB-6, dB-4dot77, dB-3, dB-1dot77, dB0, dB1, dB2, and dB3.20. A base station to perform a wireless communication in an inter-cellinterference environment, the base station comprising: a processor toestablish a Radio Resource Control (RRC) connection with a UserEquipment (UE) through a first serving cell; and a transmitter totransmit, to the UE, an RRC message through the first serving cell, theRRC message comprising cell-specific reference signal (CRS) informationof a neighbor cell and Physical Downlink Shared Channel (PDSCH)information of the neighbor cell, and the PDSCH information of theneighbor cell comprising a parameter relating to a power ratio of a CRSof the neighbor cell and a PDSCH of the neighbor cell, and to transmitthe PDSCH through the first serving cell, wherein the parameter relatingto the power ratio of the CRS of the neighbor cell and the PDSCH of theneighbor cell is configured for the UE to cancel an interference of thePDSCH of the neighbor cell in retrieving data from the PDSCH of thefirst serving cell, wherein the PDSCH information of the neighbor cellcomprises a first power parameter (p-a) and a second power parameter(p-b), wherein the RRC message comprises a NAICS_Config message, theNAICS_Config message comprising a CRS-AssistanecInfo field having theCRS information of the neighbor cell and a PDSCH-AssistanceInfo fieldhaving the PDSCH information of the neighbor cell, wherein thePDSCH-AssistanceInfo field comprises a field for the first powerparameter (p-a) and a field for the second power parameter (p-b), andwherein the field for the second power parameter (p-b) comprises atleast one of 0, 1, 2, and 3, and the field for the first power parameter(p-a) comprises at least one of dB-6, dB-4dot77, dB-3, dB-1dot77, dB0,dB1, dB2, and dB3.